The invention relates to transfer device for products, in particular aluminum cans, conveyed by means of a first transport system, which are transferred from the first transport system in groups in the form of a row aligned in the first transporting direction to a second transport system, wherein the placement of the products on the second transport system takes place in such a way that the row extends transversely in respect to its transporting direction. More particularly, the present invention relates to such a transfer device with a pickup mechanism holding the respective group of products during the transfer movement that is guided along a movement track by at least one drive linkage, wherein the drive linkage has a first arm which is pivotably connected at one end to a first shaft on the pickup mechanism and by its other end is pivotably connected to a second shaft on a rotating drive crank, and with a second arm, which is pivotably connected to a third shaft on the first arm and is pivotably connected to a fourth shaft, which is a fixed shaft.
The first transport system can be a belt, for example, on which the products are arranged in rows (in particular, single rows or double rows or several rows next to each other). The transfer device takes up respectively one section, i.e., a group, of this row or rows and transfers it to the second transport system on which the products are placed. Placement is performed with an alignment of the row or rows in such a way that the long direction of the row or rows extends transversely to the transporting direction of the second transport system. If, for example, the second transport system is also a belt, the row of products extends transversely, in particular perpendicularly, to the long extension of the belt. The products can be cans, for example, in particular beverage cans, whose exteriors are sequentially imprinted by a printing machine upstream of the first transport system and are then conveyed by means of the transport system to the transfer device. The transfer device rearranges the cans, received in groups, in such a way that they are placed on the second transport system in rows extending respectively parallel to each other, wherein the long extension of these rows lies transversely to the transporting direction of the second transport system. In this way the second transport system is provided with very densely placed products which, in case of the cans mentioned, are conveyed to a drying process, which may be continuous.
The transfer device is designed in such a way that by means of its pickup mechanism it receives products from the first transport system, wherein it moves along synchronously with the products during the pickup process, so that no or only a negligible relative movement between the products and the pickup mechanism occurs during the pickup process. This guarantees a positionally exact and therefore assured transfer at high speeds. The same applies to the depositing mode on the second transport system. Here, too, the pickup mechanism moves within a fixed movement track area synchronously or almost synchronously with the transporting means of the second transport system, so that positionally exact placement is possible without the products bumping into each other or falling over, etc. Since the transfer process must take place very rapidly because of the large number of products being delivered, it is necessary to keep the products very securely on the pickup mechanism because of the acceleration forces occurring during the transfer process. A vacuum holding device is preferably used for this; i.e., the products are attracted by suction from above and then transferred. It is not necessary for the pickup mechanism to change its position in height for this for it can move on one level. During pickup, it is sufficient for an attraction process if it is at a slight distance above the upper edges of the cans. Correspondingly the same applies for depositing, wherein the depositing process is achieved in that the vacuum is turned off and the products are released by this and deposited on the second transport system.
A transfer device of the above described type is known from European Patent Application 0 563 461. This known transfer device has the disadvantage that very high acceleration forces act on the machine frame during operation, resulting in uneven running not free of vibrations which, on the one hand, causes great stress on the material and, on the other, makes positionally exact pickup and deposit of the products difficult. In addition, pickup and deposit by means of a vacuum is not optimal in the device disclosed in that application.
Another similar transfer device is shown in U.S. Pat. No. 3,958,683. This transfer device also has the disadvantage of the very high acceleration forces that act upon the machine frame during operation. A motor or other driving force associated with this transfer device must be designed to provide the greatest acceleration necessary to accomplish the transfer, and also to overcome inertia forces when the direction of the transfer device movement is changed.
The transfer device of U.S. Pat. No. 5,311,978 recognizes this problem and, to allow use of a smaller motor for power, provides the drive means with a flywheel assembly. The flywheel provides counter-inertia to allow a smaller motor to suffice to overcome the inertia when the transfer device changes direction, and provides additional drive to boost acceleration when needed. Inclusion of the flywheel also requires additional moving parts in the transfer device.
Use of a smaller motor helps to reduce some of the stresses induced in the transfer device. However, there are still considerable forces acting upon the first and second arm, which result in vibration and stress of the transfer device.